Optical pick-up actuator using a concentrated magnetization

1. An actuator for optical pick-up using a concentrated magnetization method, comprising: a lens holder attached to an objective lens; a coil wound around the lens holder to receive a current; and permanent magnet means for constructing a magnetic circuit along with the coil so as to move the objective lens, the magnet means being magnetized in such a manner to concentrate a magnetic flux on the effective surface of the coil, wherein the permanent magnet means includes: an upper-piece magnet having its anisotropic direction inclined downwards; and lower-piece magnet adhered to the upper-piece magnet in such a manner to have its anisotropic direction inclined upwards.

2. The actuator as claimed in claim 1 , wherein the coil includes: a focusing coil wound around the circumference of the lens holder to move the objective lens in the upward and downward direction; and a tracking coil attached to the circumference surface of the focusing coil to move the objective lens in the left and right direction, the tracking coil being opposed to the permanent magnet means.

3. The actuator as claimed in claim 1 , wherein the permanent magnet means is magnetized in a state of orienting its anisotropic direction toward the coil in such a manner that a magnetic flux concentrates on the effective surface of the coil.

4. The actuator as claimed in claim 1 , wherein the upper-piece magnet and the lower-piece magnet are made from a sintered magnet.

5. The actuator as claimed in claim 1 , wherein the upper- piece magnet and the lower-piece magnet are adhered to each other in such a manner that their anisotropic directions each concentrate on the effective surface of the coil and then are grounded into a square shape.

6. An actuator for optical pick-up using a concentrated magnetization method, comprising: a lens holder attached to an objective lens; a focusing coil wounded around the lens holder; a tracking coil adhered to the focusing coil to receive a current in a direction perpendicular to a direction of a current applied to the focusing coil; permanent magnet means for constructing a magnetic circuit along with the coils, the magnet means being magnetized in such a manner to concentrate a magnetic flux on the effective surfaces of the tracking coil and the focusing coil; yoke for guiding a magnetic flux generated at the permanent magnet means into the tracking coil and the focusing coil; a frame for supporting the yoke and the permanent magnet means; and an elastic member for delivering currents applied to the tracking coil and the focusing coil and for stably supporting the lens holder upon movement of the objective lens, wherein the permanent magnet means includes: an upper-piece magnet having its anisotropic direction inclined downwards; and a lower-piece magnet adhered to the upper-piece magnet in such a manner to have its anisotropic direction inclined upwards.

7. The actuator as claimed in claim 6 , further comprising: a bobbin circuit board being electrically connected to the tracking coil, the focusing coil and the elastic member and secured to the lens holder to apply a current from the elastic member to the tracking coil and the focusing coil; and a frame circuit board being secured to the frame and electrically connected to the elastic member to receive a servo signal from the exterior.

8. The actuator as claimed in claim 6 , wherein the permanent magnet means is magnetized in a state of orienting its anisotropic direction toward the coil in such a manner that a magnetic flux concentrates on the effective surface of the coil.

9. The actuator as claimed in claim 6 , wherein the upper-piece magnet and the lower-piece magnet are made from a sintered magnet.

10. The actuator as claimed in claim 6 , wherein the upper-piece magnet and the lower-piece magnet are adhered to each other in such a manner that their anisotropic directions each concentrate on the effective surface of the coil and then are grounded into a square shape.

11. An optical pick-up actuator, comprising: a lens holder attached to an objective lens; a coil wounded around the lens holder to receive a current; and permanent magnet means for constructing a magnetic circuit along the coil so as to move the objective lens, the permanent magnet means comprising a plurality of anisotropic magnets wherein the permanent magnet means includes: an upper-piece magnet having its anisotropic direction inclined downwards; and a lower-piece magnet adhered to the upper-piece magnet in such a manner to have its anisotropic direction inclined upwards.

12. The actuator as claimed in claim 11 , wherein the coil includes: a focusing coil wound around the circumference of the lens holder to move the objective lens in the upward and downward direction; and a tracking coil attached to the circumference surface of the focusing coil to move the objective lens in the left and right direction, the tracking coil being opposed to the permanent magnet means.

13. The actuator as claimed in claim 11 , wherein the permanent magnet means is magnetized in a state of orienting its anisotropic direction toward the coil in such a manner that a magnetic flux concentrates on the effective surface of the coil.

14. The actuator as claimed in claim 11 , wherein the upper-piece magnet and the lower-piece magnet are made from a sintered magnet.

15. The actuator as claimed in claim 11 , wherein the upper- piece magnet and the lower-piece magnet are adhered to each other in such a manner that their anisotropic directions each concentrate on the effective surface of the coil and then ate grounded into a square shape.